Calculation of ADC sampling rate

[manishbaing2789]

Posted on November 19, 2013 at 09:11

Hello,

♯ I am working with STM32F4 Discovery  and summon arm tool chain.I am sending ADC  data over       serial Port using USB serial communication.

♯ I have write code to get ADC value in continuous conversion mode.Its working fine.

Now I have to ADC sampling rate by using ADC configuration parameters

 I have read stm32f4 reference manual but i didn't get any exact formula regarding that.

So how should I calculate it ..?

   is there any formula for calculation of sampling rate..? if  so then please mention link of referred      Document .

following is my ADC configuration code where I have set

ADC_CommonInitStructure.ADC_Prescaler = ADC_Prescaler_Div4;

.ADC_CommonInitStructure.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles;

...............................ADC Configuration......................

/*! ADC source File */&sharpinclude ''stm32f4xx.h''&sharpinclude ''/home/manish/Product_codes/Verified-Codes/my-usb-with-adc-24-sept/STM32F4_USB_CDC/libs/STM32F4xx_StdPeriph_Driver/inc/stm32f4xx_adc.h''&sharpinclude ''/home/manish/Product_codes/Verified-Codes/my-usb-with-adc-24-sept/STM32F4_USB_CDC/libs/STM32F4xx_StdPeriph_Driver/inc/stm32f4xx_rcc.h''&sharpinclude <math.h>&sharpinclude <stdio.h>&sharpinclude <stdlib.h>/*! ADC Initialazion function */adcInit(){     RCC_ClocksTypeDef RCC_Clocks;    /*! Intialsizing structure to set ADC Configuration */    ADC_InitTypeDef ADC_InitStructure;    /*! Intialsizing structure to set GPIO  Configuration */ GPIO_InitTypeDef GPIO_InitStructure;    /*! Intialsizing structure to set ADC  Common Configuration */ ADC_CommonInitTypeDef ADC_CommonInitStructure;         /*! Enable ADC1 Interface Clock */ RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);//..................................................        RCC_AHB1PeriphClockCmd(RCC_AHB1ENR_GPIOCEN,ENABLE);//...................................................        RCC_GetClocksFreq(&RCC_Clocks); /*! Enable the ADC1 GPIO Clock */      //RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);  /*! Initializing GPIO for ADC */ GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2; GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN; GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz; GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL; /*! Configuring  ADC GPIO pins in analog mode */ GPIO_Init(GPIOC, &GPIO_InitStructure); /*! ADC Common Init */ /*! Use Independent mode */ ADC_CommonInitStructure.ADC_Mode = ADC_Mode_Independent;// ADC_CommonInitStructure.ADC_Prescaler = ADC_Prescaler_Div2;        ADC_CommonInitStructure.ADC_Prescaler = ADC_Prescaler_Div4; ADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled; ADC_CommonInitStructure.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles; /*!  *  Initializes the ADCx peripheral according  *  to the specified ADC parameters in the ADC_CommonInitStruct */ ADC_CommonInit(&ADC_CommonInitStructure);  /*! ADC1 Init */ ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b; ADC_InitStructure.ADC_ScanConvMode = DISABLE; ADC_InitStructure.ADC_ContinuousConvMode = ENABLE; ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;        ADC_InitStructure.ADC_ExternalTrigConv = 0; ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right; ADC_InitStructure.ADC_NbrOfConversion = 1; /*! *  Initializes the ADCx peripheral according  *   to the specified ADC parameters in the ADC_InitStruct.          */       ADC_DeInit(); ADC_Init(ADC1, &ADC_InitStructure); /*! Enabling Temperature sensor */ //ADC_TempSensorVrefintCmd(ENABLE); /*! ADC1 regular channel16 configuration */ //ADC_RegularChannelConfig(ADC1, ADC_Channel_1, 1, ADC_SampleTime_3Cycles);        ADC_RegularChannelConfig(ADC1, ADC_Channel_16, 1, ADC_SampleTime_144Cycles); /*! Enable(Activate ) ADC1 Peripherals */ ADC_Cmd(ADC1, ENABLE);       ADC_ContinuousModeCmd(ADC1, ENABLE);     /*! Intialsizing structure For NVIC Configuration */ NVIC_InitTypeDef NVIC_InitStructure;         /*! set parameters of NVIC_InitTypeDef structure */ NVIC_InitStructure.NVIC_IRQChannel = ADC_IRQn; NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0; NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; /*! * Initializes the NVIC peripheral according *  to the specified parameters in the NVIC_InitStruct */ NVIC_Init(&NVIC_InitStructure);} #adc-sampling-rate

[Tesla DeLorean]

Posted on November 19, 2013 at 10:41

I'm sure the manual describes the relationship between the ADC clock the sample time, conversion time (12-cycles?), etc.

If reading is not your thing, a more practical approach to confirm the calculation, or actual rate, then one could toggle a GPIO at the EOC and measure the time on a scope, or at the interrupt read the value of a free running timer or counter. The core's cycle counter being particularly good timebase in this regard.